One of the most time and resource consuming steps in the making of an electronically scanned array antenna is the calibration of its elements with respect to each other. All of the elements across the array must be calibrated to a known amplitude and phase to form a beam. This process is referred to as array phase-up.
Conventional phase-up techniques typically require the use of external measurement facilities such as a nearfield range to provide a reference signal to each element in receive and to measure the output of each element in transmit. As all the elements must be operated at full power to provide the full transmit plane wave spectrum to sample, a great deal of energy is radiated during this testing. This dictates some implementation of high RF power containment, and carries with it a number of safety concerns.
Known array mutual coupling phase up techniques have been dependent on two dimensional symmetric lattice arrangements (equilateral triangular) and equal element mutual coupling responses in all lattice orientations. These are serious limitations since equilateral triangular lattice arrangements are not always used. Similarly, the element mutual coupling response is most often not equal in all lattice orientations.
Previous discussions of array self-calibration have noted the need for separate transmit and receive feeds to support the simultaneous transmit/receive operation required for calibration.